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      <title>怎么预防死锁？ - 交互式测验</title>
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    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>怎么预防死锁？ - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
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                <div class="quiz-footer" id="quiz-footer">
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  {
    "question": "根据文档，死锁的发生必须同时满足四个必要条件。以下哪一项不属于这四个必要条件之一？",
    "options": [
      "持有并等待条件 (Hold and Wait)",
      "高优先级抢占条件 (High Priority Preemption)",
      "互斥条件 (Mutual Exclusion)",
      "循环等待条件 (Circular Wait)"
    ],
    "correctAnswerIndex": 1,
    "explanation": "死锁的四个必要条件是：互斥条件、持有并等待条件、不可剥夺条件和循环等待条件。'高优先级抢占'不是死锁发生的必要条件，而'不可剥夺'（No Preemption）才是其中之一，它指的是资源不能被强制性地从持有者手中夺走。",
    "source": "文档中「死锁的定义与成因」-「成因」部分",
    "hint": "回顾一下死锁成因部分提到的四个以'条件'结尾的术语。"
  },
  {
    "question": "在死锁预防策略中，规定所有线程必须按照相同的、预先定义的顺序来请求资源，这种方法主要是为了破坏死锁的哪个必要条件？",
    "options": [
      "循环等待条件 (Circular Wait)",
      "互斥条件 (Mutual Exclusion)",
      "不可剥夺条件 (No Preemption)",
      "持有并等待条件 (Hold and Wait)"
    ],
    "correctAnswerIndex": 0,
    "explanation": "通过对系统中的所有资源进行全局排序，并要求线程严格按照资源的顺序进行请求，可以确保资源请求形成一个有向无环图，从而从根本上消除了形成循环等待链的可能性。这是破坏'循环等待条件'的经典策略。",
    "source": "文档中「死锁的预防策略」-「4. 破坏循环等待条件」部分",
    "hint": "思考一下，如果所有人都按从1到10的顺序拿东西，会不会出现A等B拿2号，B等A拿1号的情况？"
  },
  {
    "question": "当系统无法完全避免死锁时，可以采用一种策略，即通过构建一个包含进程和资源节点的图，并检测图中是否存在环路来判断死锁。这种策略属于什么范畴？",
    "options": [
      "死锁恢复 (Deadlock Recovery)",
      "死锁预防 (Deadlock Prevention)",
      "死锁检测 (Deadlock Detection)",
      "乐观并发控制 (Optimistic Concurrency Control)"
    ],
    "correctAnswerIndex": 2,
    "explanation": "这种方法被称为基于资源分配图（Resource Allocation Graph, RAG）的死锁检测算法。它并不预防死锁的发生，而是在系统运行时定期检查是否存在死锁状态，这属于'死锁检测'的范畴。检测到死锁后，才会进入'死锁恢复'阶段。",
    "source": "文档中「死锁检测与恢复」-「2. 死锁检测算法」部分",
    "hint": "这种策略是在问题可能发生后去'寻找'它，而不是在问题发生前去'阻止'它。"
  },
  {
    "question": "在检测到系统发生死锁后，需要采取恢复策略。以下哪一项不属于文档中提到的死锁恢复策略？",
    "options": [
      "回滚 (Rollback) 某个或某些事务",
      "一次性分配所有资源给优先级最高的进程",
      "终止 (Terminate) 一个或多个进程",
      "资源剥夺 (Resource Preemption)"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档中提到的死锁恢复策略主要有三种：回滚、终止进程和资源剥夺。'一次性分配所有资源'是一种'死锁预防'策略，用于破坏'持有并等待'条件，它在任务执行前进行，而不是在死锁发生后作为恢复手段。",
    "source": "文档中「死锁检测与恢复」-「3. 死锁恢复策略」部分",
    "hint": "注意区分'预防'措施和'恢复'措施，前者在事前，后者在事后。"
  },
  {
    "question": "针对分布式系统中可能出现的死锁问题，文档中提到的“锁租约（Lease）机制”和“锁超时机制”主要是为了解决什么问题？",
    "options": [
      "防止因某个节点持有锁时间过长或崩溃而导致系统永久死锁。",
      "确保所有分布式节点的数据完全一致。",
      "减少网络通信延迟对锁性能的影响。",
      "实现跨多个系统的事务原子性。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "在分布式环境中，如果一个持有锁的节点崩溃或无法通信，它持有的锁可能永远无法释放。锁超时和锁租约机制可以确保锁在一定时间后自动释放，从而避免了因节点故障导致的永久死锁，增强了系统的健壮性。",
    "source": "文档中「常见的死锁场景分析」-「5. 跨系统分布式锁死锁」部分",
    "hint": "想一想，如果一个服务拿着钥匙后突然消失了，系统该怎么办？"
  },
  {
    "question": "根据文档，“破坏持有并等待条件”的一种策略是要求线程在执行前一次性获取所有需要的资源。这种策略存在什么主要的挑战或缺点？",
    "options": [
      "增加了实现资源排序的复杂性。",
      "容易导致资源利用率降低，因为资源可能被长时间闲置。",
      "无法应用于数据库事务中。",
      "会显著增加死锁检测的系统开销。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档明确指出，一次性分配所有资源的策略可能导致资源利用率降低。因为一个线程可能很早就获取了所有资源，但其中一些资源直到执行的后期阶段才会被使用，在这期间这些资源处于被占用但闲置的状态，无法被其他线程利用。",
    "source": "文档中「死锁的预防策略」-「2. 破坏持有并等待条件」部分",
    "hint": "想象一下，为了做一顿饭，你必须在一开始就把一整天需要的所有厨具和食材都拿到手，这会对厨房的使用效率产生什么影响？"
  },
  {
    "question": "在数据库场景中，当事务A锁定了表1的某行并试图更新表2，同时事务B锁定了表2的某行并试图更新表1时，这种情况最符合哪种死锁场景的描述？",
    "options": [
      "嵌套锁导致的死锁",
      "资源竞争死锁",
      "信号量和锁组合使用导致的死锁",
      "跨系统分布式锁死锁"
    ],
    "correctAnswerIndex": 1,
    "explanation": "这个场景是典型的资源竞争死锁，也被称为数据库死锁。两个事务分别持有一部分资源（锁定的行），同时又请求对方持有的资源，形成了循环等待，导致死锁。其本质是由于资源的竞争和不一致的锁定顺序导致的。",
    "source": "文档中「常见的死锁场景分析」-「1. 资源竞争死锁」及「4. 数据库死锁」部分",
    "hint": "这个场景的核心是两个实体（事务）互相请求对方已经占有的资源。"
  }
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                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  